This invention relates to a bulked continuous filament nylon yarn and in particular to a process for producing bulked continuous filament nylon yarn having adjacent sections of different bulk levels with improved coherency.
Synthetic continuous filament yarns which have been intermittently bulked along their length are well known. Various bulking methods have been employed such as false-twist crimping, stuffer-box crimping, edge crimping, and jet crimping, each of the bulking methods being applied to the yarn intermittently so as to leave certain lengths of yarn unbulked. Where heat is used for bulking, such processes not only create contrasts in bulk between the bulked and unbulked zones but also differences in luster and dyeability, the heated bulked zones conventionally having deeper dyeability due to the relaxation which takes place. It is also known to reduce or remove bulk or latent bulk development potential intermittently from a previously bulked yarn by intermittently pressing a bulked yarn under tension against a heated shoe, or by treating various types of bulked yarns intermittently with a swelling agent and then passing such treated yarn under tension through a heating zone to release the bulk in the treated parts of the yarn. However, when yarns are intermittently debulked before being made into a fabric, the filaments in the debulked zone have little entanglement and cohesion and are likely to snag when being used in fabric-making operations causing operating difficulties and fabric defects. Therefore, a rapid continuous method of intermittently reducing or removing bulk development capability from the filaments of bulked yarns and at the same time introducing sufficient coherency for adequate handling is highly desirable.
One method for providing a coherent multi-filament yarn is taught by Bunting and Nelson in their U.S. Pat. No. 3,110,151. According to the patent interlaced yarn is produced by passing a multifilament strand or plurality of strands, under a controlled positive tension sufficient to prevent formation of ring-like loops, through a fluid jet which separates filaments and groups of filaments from each other and then randomly intermingles them.